Comparisons of nutrient recovery and specific leaf area variation between Carex lasiocarpa var. occultans and Carex thunbergii var. appendiculata with reference to nutrient conditions and shading by Phragmites australis

The distribution of two sedge species was studied in two mires which differ in abiotic environments and in distribution of Phragmites australis. Carex lasiocarpa var. occultans dominated in nutrient‐poor valley mire, and Carex thunbergii var. appendiculata dominated in nutrient‐rich flood plain subject to water fluctuations. Phragmites australis grew well in nutrient‐rich conditions. The distribution of C. lasiocarpa showed a strong negative correlation with P. australis coverage, whereas C. thunbergii coverage was not affected by P. australis . The leaf area per dry leaf mass (specific leaf area: SLA) of C. thunbergii increased with shading by P. australis , but that of C. lasiocarpa was stable. The SLA flexibility of C. thunbergii to light interception might enable this species to invade P. australis patches in nutrient‐rich environments. The residual nutrient ratio of nitrogen and phosphorus (the ratio of the residual nutrient content at the end of the growing season to peak nutrient content) in the vegetative ramet of C. thunbergii was 1.7 times higher than that of C. lasiocarpa . This low residual ratio may indicate effective nutrient recovery to storage organs. The effective nutrient recovery in C. lasiocarpa might enable this species to grow even in nutrient‐poor environments. However, it may be difficult for C. lasiocarpa to expand its habitat to nutrient‐rich areas where P. australis dominates as it is not shade tolerant.